The present invention is related to pneumatic distributors for the control of railway vehicle brakes and particularly to such distributors as operate on the pressure proportioning principle popularized in Europe, as opposed to the pressure equalization principle on which operation of conventional triple valves used for freight service in this country is based.
Pneumatic distributors of the pressure proportioning type are commonly referred to as being self-lapping in operation in that a differential control force on the control piston abutment of the piston valve assemblage urging movement of the assemblage to a position opening its supply valve is in turn counteracted by the delivery pressure via the supply valve acting on a reaction piston abutment of the assemblage to urge movement back to close the supply valve when the force balance is reestablished.